1. Technological Field
The present invention relates to an image forming system, a method for controlling an image forming system, and a paper conveyance processing apparatus.
2. Description of the Related Art
There has been generally known an image forming system in which an image forming apparatus and one or more post-processing apparatuses are connected to each other. In such a system, during conveyance of paper, an abnormality may occur in any apparatus. An apparatus in which an abnormality has been detected (hereinafter, referred to as a “causing apparatus”) stops operating.
In this case, apparatuses, other than the causing apparatus in the image forming system, are respectively controlled such that waste of paper and processes does not occur. See Japanese Patent Publication No. 2007-210775. In this technique, an apparatus positioned on an upstream side of the causing apparatus on the paper conveyance (hereinafter, referred to as an “upstream apparatus”) is notified of an abnormality from the causing apparatus and stops the conveyance of paper to the causing apparatus.
On the other hand, an apparatus positioned on a downstream side of the causing apparatus on the paper conveyance (hereinafter, referred to as a “downstream apparatus”) may continue performing operation, such as paper conveyance, in order to prevent paper being processed from being wasted. For example, in a case where paper is conveyed across the causing apparatus and the downstream apparatus, when the causing apparatus stops, the paper spanning the causing apparatus and the downstream apparatus (hereinafter, referred to as a “crossing paper”) may be drawn out to the downstream apparatus, which continues the conveyance, from the causing apparatus having stopped the conveyance.
However, a part of the crossing paper is positioned inside the causing apparatus. Therefore, the crossing paper may be not paper subjected to all processes of the causing apparatus (hereinafter, referred to as an “effective paper”), and may be paper not subjected to some processes (hereinafter, referred to as an “ineffective paper”).
Since the downstream apparatus is not able to know whether the crossing paper is the effective paper or the ineffective paper, the downstream apparatus performs the same process for all of the effective paper and the ineffective paper. Therefore, since the downstream apparatus performs a normal process for the ineffective paper to be discarded later, there is a problem that wasteful processing occurs.
Furthermore, the effective paper and the ineffective paper continuously conveyed are discharged to the same paper discharge tray. Consequently, a user is required to confirm whether there is the ineffective paper among output objects. Moreover, when the user is not able to easily determine the presence or absence of the ineffective paper, there is also a problem that waste of paper occurs, since it is necessary to perform printing again.